Stored Procedure refuses to delete column that it creates

I've created a Stored Procedure that refreshes the data in a table. It first re-loads the entire table. Next, several filters are applied. (Example: the column 'Model' must equal 'W'; all rows with model 'B' are deleted.) This happens after the table has been loaded (and not during) because I want to log how many rows are deleted because of each individual filter. After the filters have been applied, some columns contain the same value in every row (the other values were deleted in the filtering process). These columns are now useless, so I want to delete them.

This seems to be problematic for SQL Server. When given the command to execute the SP, it indicates that the columns it is supposed to remove in its final step do not currently exist and refuses to run. That is technically correct, the columns currently don't exist, but they will be created by the SP itself.